1. Field of the Invention
The present invention relates to a nuclear magnetic resonance diagnostic apparatus (to be referred to as an "NMR diagnostic apparatus" hereinafter) which utilizes the magnetic resonance phenomenon so as to noninvasively measure information as to the density and relaxation time of a specific atomic nucleus or proton within a selected sectional slice plane of an object to be examined, e.g., a patient, for which a tomographic image is taken, and to display information for medical diagnosis in the form of tomographic images.
2. Description of the Prior Art
In a conventional NMR diagnostic apparatus, a tomographic image plane (i.e., selected sectional slice plane) in a patient to be examined is limited to a plane which intersects a central point defined by gradient magnetic coils at which the strength of the gradient magnetic field is zero. For this reason, in order to obtain a plurality of adjacent sagittal images, the patient must be mechanically moved to the central point for each imaging. With such a conventional NMR diagnostic apparatus, a long time is generally required to collect data for obtaining one specific tomographic image by rotating the gradient direction of a gradient magnetic field at 360.degree. in a plane perpendicular to the longitudinal axis of the patient with respect to the selected sectional slice plane of which a tomographic image is taken. Accordingly when more than one tomographic image is to be obtained, a still longer data collection time is required, resulting in a heavier imposition on the patient and disturbance in fast diagnosis.
The present invention has been made in consideration of the conventional drawbacks, and has for its object to provide a nuclear magnetic resonance diagnostic apparatus which does not require mechanical movement of a patient with respect to the longitudinal axis thereof during NMR signal collection, which is capable of obtaining tomographic images in any direction and at any portion of the patient, and which allows adoption of the multi-slice method.